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It is the purpose of the author to define 'inter-psychology' with a view to substituting that term for 'social' psychology; and to outline a programme for the development of that science. As for the use of terms, it is claimed that 'inter-psychology' is at once more 'general and exact than 'social' or 'collective' psychology. It is more general because it includes, in addition to social relations, mental relationships with other minds which are not social. Mental relationships of the latter sort are the study of animals or men without entering into social relationship with them. The term is more exact because it clearly marks the character of the facts studied by social psychology. The peculiar character of these facts consists in their being psychological phenomena produced in one mind by encounter with another mind. As for the programme of inter-psychology, T. states that it has its own method and materials. Its method is the genetic method, since the study of the social relations of the child throw light on the social relations of the adult. Its materials are feelings, ideas, plans, desires, and beliefs. These constitute the materials of inter-psychology because they are communicable; sensations are excluded because they are not communicable. A thorough treatment of the subject would have to answer the questions, why some feelings are propagated in a given environment, at a given time; by what methods they are propagated; what transformations they undergo. In the propagation of feelings, five cases are distinguished. First, the influence of one individual on another, as in conversation; second, the influence of an individual on a crowd; third, the influence of a crowd on an individual, as in timidity; fourth, the influence of an individual on a public; fifth, the influence of a public on an individual. Inter-psychology possesses in statistics an instrument for exact measurement which, it is true, must be used with great care.

It is a matter of no small moment whether the development of concepts is due to external causes or to the mind's spontaneous activity. The psychogenesis of extension is scarcely touched upon by the nativistic and empiristic theories of spatial determinations, both of which are concerned rather with the physiological question of localization. The former theory—which is really Kant's doctrine applied to physiology was first advanced by Müller; the latter by Helmholtz. The nativist postulates a special optical mechanism; owing to the natural endowment of the various retinal points, tridimensional space perception is a part of every visual sensation. According to the empiricist, such sensations are merely signs which